Active material head restraint assembly

ABSTRACT

A head restraint assembly is provided that is movable between a retracted position and a deployed position. The head restraint assembly includes a support member and a deployable member. A link is rotatably mounted with respect to the support member and the deployable member. A shaft is mounted to the link for rotation therewith. The active material is actuatable to rotate the shaft and thereby cause the deployable member to move from its retracted position to its deployed position.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/056,659 filed on Mar. 27, 2008, which claims the benefit ofU.S. Provisional Patent Application No. 60/911,314, filed Apr. 12, 2007,and which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to a head restraint in automotive vehicles, andmore particularly to latching and deployment of the head restraint usingan active material.

BACKGROUND OF THE INVENTION

Head restraint assemblies are commonly employed in vehicles and aretypically adjustably attached to the seatback. The head restraint is inalignment with the back of a seated occupant's head to provide comfort,support, and protection during operation of the vehicle. The paddedportion of the head restraint that is adapted to provide the support andprotection is typically positioned by the end-user.

Occupants of a vehicle tend to position their seat backs at differentangles for comfort. For example, vehicle occupants tend to sit moreupright in vehicles with higher seating heights such as vans and sportutility vehicles whereas in passenger cars the occupants tend to be in amore reclined position. The changes in seat back position can move theattached head restraint further or closer to the head of the seatedoccupant. That is, the space between an occupant's head and the headrestraint can be affected and altered by the seat back position.

SUMMARY OF THE INVENTION

In some situations it may be desirable for the head restraint to beclose to or touching the back of the occupant's head. During vehicle useit may be desirable to adjust the head restraint assembly from aposition selected based upon comfort to a position that is based uponsupport for the occupant.

A head restraint assembly is provided which includes a support memberand a deployable member selectively movable between a refracted positionand a deployed position. The deployable member is farther from thesupport member in the deployed position than in the retracted position.A link is rotatably mounted with respect to the support member androtatably mounted with respect to the deployable member. The headrestraint assembly further includes a shaft that is mounted to the linkfor rotation therewith. An active material member has first and secondends mounted with respect to the support member. A center portion of theactive material member engages a lip on the shaft such that the activematerial member is characterized by a curved shape, with the ends onopposite sides of the lip. The active material is actuatable to rotatethe shaft and thereby cause the deployable member to move from itsretracted position to its deployed position.

An alternative head restraint assembly uses a clutch assembly slidinglyengaged with a rod for translation. A second link is rotatably mountedwith respect to the deployable member and the clutch assembly. Movementof the deployable member from its refracted position to its deployedposition causes the second link to rotate such that the clutch assemblytranslates along the rod. The second link and rod create a frame supportfor the member, giving it a more stable configuration and higher loadcapacity when an object makes contact with the padded member.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a passenger compartment having aseat assembly with a head restraint assembly;

FIG. 2 is a rear schematic view of the head restraint assembly of FIG. 1in a restrained position;

FIG. 2A is a side schematic view of the head restraint assembly of FIGS.1 and 2 in the restrained position;

FIG. 3 is a rear schematic view of the head restraint assembly of FIGS.1-2A in a deployed position;

FIG. 3A is a side schematic view of the head restraint assembly of FIGS.1-3 in the deployed position;

FIG. 4 is a side schematic view of another embodiment of a headrestraint assembly for use with the seat assembly of FIG. 1 in arestrained position;

FIG. 5 is a side schematic view of the head restraint assembly of FIG. 4in a partially deployed position;

FIG. 6 is a side schematic view of the head restraint assembly of FIGS.4 and 5 in a fully deployed position;

FIG. 7 is a schematic illustration of a clutch assembly used in the headrestraint assembly of FIGS. 4-6 in a nominal position;

FIG. 8 is a schematic illustration of the clutch assembly of FIG. 7 inan upwardly driven second position;

FIG. 9 is a schematic illustration of the clutch assembly of FIGS. 7 and8 in a locked third position;

FIG. 10 is a schematic illustration of the clutch assembly of FIGS. 7-9in a disengaged fourth position;

FIG. 11 is a schematic illustration of the clutch assembly of FIGS. 7-10in a downwardly driven fifth position;

FIG. 12 is a rear schematic view of another embodiment of a headrestraint assembly for use with the seat assembly of FIG. 1 in arestrained and latched position;

FIG. 13 is a rear schematic view of the head restraint assembly of FIG.12 in a restrained and unlatched position;

FIG. 14 is a rear schematic view of the head restraint assembly of FIGS.12 and 13 in a restrained and unlatched position; and

FIG. 15 is a rear schematic view of the head restraint assembly of FIGS.12-14 in a deployed position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like reference numbers refer to likecomponents, FIG. 1 schematically depicts, a seat assembly 10 mounted tothe floor 14 of a vehicle body 18. The vehicle body 18 defines apassenger compartment 22 in which the seat assembly 10 is disposed. Theseat assembly 10 includes a lower seat portion 26, a seatback portion30, and a head restraint assembly 34. The lower seat portion 26 definesa generally horizontally-oriented surface 38 for supporting an occupant(not shown). The seatback portion 30 is mounted with respect to thelower seat portion 26, and defines surface 42 for supporting the back ofthe occupant. The seatback portion 30 may be rigidly mounted withrespect to the lower seat portion 26, or may be rotatably mounted withrespect to the lower seat portion 26 so that the reclination angle isselectively variable by the occupant.

The head restraint assembly 34 is mounted to the upper end of theseatback portion 30. The head restraint assembly 34 is depicted as aseparate member from the seatback portion; however, it should be notedthat, within the scope of the claimed invention, a head restraintassembly may be an integral part of a seatback portion as understood bythose skilled in the art. For example, a head restraint may be the upperportion of a seatback. The head restraint assembly 34 defines a surface46 that faces generally the same direction as surface 42.

Referring to FIGS. 2 and 2A, head restraint assembly 34 includes asupport member, such as plate 54, that is mounted with respect to theseatback portion (shown at 30 in FIG. 1), and a padded member 58 thatdefines surface 46. The padded member 58 is operatively connected to theplate 54 by an actuator assembly 62 that is configured to selectivelymove the padded member 58 with respect to the plate 54. The actuatorassembly 62 includes four brackets 66A-D mounted to the plate 54, andfour brackets 70A-D mounted to the padded member 58. Four links 74A-Doperatively interconnect the plate 54 and the padded member 58. Itshould be noted that padded member 58 is exemplary; member 58selectively moves the surface 46 (shown in FIG. 1) of the head restraintassembly 34 and may have other configurations within the scope of theclaimed invention. Surface 46 may be formed by an elastic membraneoperatively connected to a member 58, etc.

More specifically, link 74A is rotatably connected to the bracket 66A atone end for rotation with respect to the plate 54 about axis A1, andlink 74A is rotatably connected to the bracket 70A at the other end forrotation with respect to the padded member 58 about axis A2; link 74B isrotatably connected to the bracket 66B at one end for rotation withrespect to the plate 54 about axis A1, and link 74B is rotatablyconnected to the bracket 70B at the other end for rotation with respectto the padded member 58 about axis A2; link 74C is rotatably connectedto the bracket 66C at one end for rotation with respect to the plate 54about axis A3, and is rotatably connected to the bracket 70C at theother end for rotation with respect to the padded member 58 about axisA4; and link 74D is rotatably connected to the bracket 66D at one endfor rotation with respect to the plate 54 about axis A3, and isrotatably connected to the bracket 70D at the other end for rotationwith respect to the padded member 58 about axis A4. Axes A1, A2, A3, A4are parallel.

The padded member 58 is depicted in a first position, i.e. retractedposition, with respect to the plate 54 in FIGS. 2 and 2A. When thepadded member 58 is in the first position, links 74A-C are generallyvertically oriented such that the brackets 70A-D abut the plate 58.

The actuator assembly 62 further includes a shaft 90 that is mounted tothe links 74A, 74B for rotation therewith about axis A1. Shaft 90 isgenerally cylindrical and is characterized by a lip 94 that protrudesradially therefrom. The actuator assembly 62 also includes a shapememory alloy (SMA) wire 98 characterized by a first end 102 and a secondend 106. The first and second ends 102, 106 are mounted to the plate 54at opposite sides thereof. The central portion of the SMA wire 98contacts the lip 94. The lip 94 is higher than the mounting locations ofends 102, 106 so that the SMA wire 98 is characterized by a “bowstring”shape, as shown in the Figures.

A shape memory alloy is characterized by a cold state, i.e., when thetemperature of the alloy is below its martensite finish temperatureM_(f). A shape memory alloy is also characterized by a hot state, i.e.,when the temperature of the alloy is above its austenite finishtemperature A_(f). An object formed of the alloy may be characterized bya predetermined shape. When the object is pseudo-plastically deformed inthe cold state, the strain may be reversed by heating the object aboveits austenite finish temperature A_(f), i.e., heating the object aboveits A_(f) will cause the object to return to its predetermined shape asthe material changes phase from Martensite to Austenite. An SMA'smodulus of elasticity and yield strength are also significantly lower inthe cold state than in the hot state. As understood by those skilled inthe art, pseudo-plastic strain is similar to plastic strain in that thestrain persists despite removal of the stress that caused the strain.However, unlike plastic strain, pseudo-plastic strain is reversible whenthe object is heated to its hot state.

The SMA wire 98 is characterized by a predetermined length (shape), andis configured such that it is characterized by tensile strain when thepadded member 58 is in its first position, as shown in FIGS. 2 and 2A.An activation device 99 is connected to the wire 98 to apply anactivation signal to the wire 98. When the wire 98 is heated to its hotstate, it decreases in length, exerting sufficient force on the lip 94to cause rotation of the shaft 90, and, therefore, links 74A, 74B, aboutaxis A1, as shown in FIGS. 3 and 3A. Referring to FIGS. 3 and 3A, as thelinks 74A, 74B rotate about axis A1, they cause the padded member 58 tomove away from the plate 54. The movement of the padded member 58 as aresult of the rotation of links 74A, 74B in turn causes the rotation oflinks 74C, 74D. When the SMA wire 98 is its predetermined length, thepadded member 58 is in a second position, i.e. deployed position, withrespect to the plate 54, as shown in FIGS. 3 and 3A, in which the paddedmember 58 is extended forward in the vehicle body and closer to anoccupant than in the first position.

The bowstring arrangement of the SMA wire 98 results in less SMA wireused compared to other SMA wire arrangements, and results in fasterdeployment of the padded member 58 from its first position to its secondposition. With the bowstring arrangement, the ends of the SMA wire arefixed, and so lead wires that supply current to the SMA wire need onlymove enough to accommodate movement of the ends 102, 106 that may resultfrom an object obstructing movement of the member 58 during deployment(i.e., if the ends are mounted to the plate 54 via an energy absorbersuch as a spring). There may also be conditions where the SMA wires arenot capable of deploying the head restraint assembly with enoughforce/speed. In such cases low stiffness balance springs can be attachedto the mechanism in a number of positions so that they counteract themass of padded member 58 as well as the mass of other mechanism/headrestraint components that are moved during deployment. These balancesprings may take the form of extension springs connected between linkagearms (such as between links 74A and 74C), extension springs connectingthe support to the front surface (such as between 54 and 70C), extensionsprings connecting support to linkage arms (such as between 54 and 74C),or torsion springs located at one of the linkage of support/clutch pivotpoints (such as between member 66A and link 74A).

Referring to FIG. 4, an alternative head restraint assembly 34A isschematically depicted. The head restraint assembly 34A uses a four-barparallel linkage system (mirrored on each side of the head restraint) tomove member 58 from a first position relative to plate 54 (i.e., aretracted position as shown in FIG. 4) to a second position relative tothe plate 54 (i.e., a deployed position as shown in FIG. 6).

Brackets 66A, 66C are mounted to the plate 54, and brackets 70A, 70C aremounted to the padded member 58. Link 74A is rotatably connected to thebracket 66A at one end for rotation with respect to the plate 54, andlink 74A is rotatably connected to the bracket 70A at the other end forrotation with respect to the padded member 58; link 74C is rotatablyconnected to the bracket 66C at one end for rotation with respect to theplate 54, and link 74C is rotatably connected to the bracket 70C at theother end for rotation with respect to the padded member 58.

A rod 110 is mounted to plate 54 via brackets 114. A link 116 isrotatably connected to bracket 70A at one end and is rotatably connectedto a clutch assembly 120 at the other end. Clutch assembly 120 isslidingly engaged with the rod 110 such that movement of the clutchassembly 120 is substantially limited to translation along the rod 110.Shaft 90 is mounted to link 74A for rotation therewith. Shaft 90includes lip 94. An SMA wire (not shown in FIGS. 4-6) operativelyinterconnects the lip 94 and the plate 54 in an identical manner to thatshown in FIGS. 2-3A. When the SMA wire is heated to its hot state, itcauses rotation of the shaft 90, which in turn causes rotation of link74A, and movement of the member 58 away from the plate 54. The member 58is shown in an intermediate position with respect to the plate 54 inFIG. 5, and is shown in its second position with respect to the plate 54in FIG. 6. Referring to FIGS. 5 and 6, the movement of the member 58causes the link 116 to translate the clutch assembly upward along therod 110, so that link 116 and link 74A create an A-frame support for themember 58, giving it a more stable configuration and higher loadcapacity when an object makes contact with the outer surface 46.

The clutch assembly 120 is a one-way clutch that permits movement of theclutch assembly 120 upward along the rod 110 and prevents downwardmovement of the clutch assembly 120 downward along the rod 110.Accordingly, the clutch assembly 120 prevents movement of the member 58from its second position, as shown in FIG. 6, to its first position, asshown in FIG. 4.

Referring to FIGS. 7-11, the clutch assembly 120 includes a plate 130with a hole (not shown) formed therein. The plate 130 is pivotablyconnected to member 132. The rod 110 extends through a hole in the plate130, which is mounted at an angle preserved by a spring 134. The hole inthe tilted plate 130 allows for the assembly 120 to slide freely up therod 110, as shown in FIG. 8. When the assembly 120 is loaded in thedownward direction, as shown in FIG. 9, spring 34, coupled with frictionon the rod 110, helps to further lift and rotate the plate 130 so thatit positively locks on to the rod 110, restricting any downward motionof the plate 130 and the assembly 120. The clutch assembly 120 can bereturned to its original position by rotating the plate 130, such as byapplying force F thereto (as shown in FIG. 10) to allow the plate 130and the assembly 120 to slide back down the rod 110, as shown in FIG.11.

Referring to FIG. 12, wherein like reference numbers refer to likecomponents from FIGS. 1-11, an alternative head restraint actuationassembly 34B is schematically depicted. SMA wire 98 is mounted to a bar200 at its ends 102, 106, and is engaged with the lip 94 of shaft 90 inthe “bowstring” arrangement. Pins 204A, 204B are mounted to the bar 200,and each pin 204A, 204B is connected to a respective spring 208A, 208Bthat pulls the bar 200 against stop members 210A, 210B. The springs208A, 208B are mounted at the opposing ends to plate 54 of FIG. 1. Eachpin 204A, 204B slides through a respective hole (not shown) formed in arespective member 214A, 214B. Members 214A, 214B are angled with respectto the pins 204A, 204B such that upward movement of the bar 200 ispermitted, but downward movement of the bar 200 is prevented. Theinteraction between members 214A, 214B and the pins 204A, 204B issimilar to the interaction between the plate 130 and rod 110.

When the SMA wire 98 is actuated, i.e., heated to its hot state, iturges the shaft 90 to rotate, as shown in FIG. 13, thereby moving thepadded member (shown at 58 in FIG. 2) to move from its first position toits second position. Referring to FIGS. 13 and 14, if an objectobstructs the padded member and prevents its movement from the firstposition to the second position, then the force of the SMA wire 98, whenit is heated to its hot state, causes the springs 208A, 208B to elongateso that the bar 200 is moved upward, as shown in FIG. 15. The bar 200would then be prevented from returning downward unless the members 214A,214B are shifted. The springs 208A, 208B thus provide strain relief. Astrain relief mechanism such as described can be reset to its originalconfiguration if engaged during deployment of the head restraint so thatthe mechanism can be deployed at a subsequent time. The resetting of thestrain relief can be done automatically using a mechanical interaction.For example, members 214A, 214B can be forced to their “disengaged”position (similar to FIG. 10), by protruding members rigidly attached torotating shaft 90. When in the retracted position, these protrusionswould keep members 214A, 214B disengaged. As they rotate outward andupward (into the page), the protrusions would no longer restrict theposition of members 214A, 214B, allowing the one-way operation of thestrain relief device. If the shaft and protrusions are rotated to theiroriginal orientation, the protrusions would again contact members 214A,214B, disengaging them. Once disengaged the stretched springs 208A, 208Bwould be free to contract, pulling bar 200 back down to its originalposition against the stops 210A, 210B.

Shape memory alloy wires are employed in the embodiments herein.However, other active materials may be employed within the scope of theclaimed invention. For example, other shape memory materials may beemployed. Shape memory materials, a class of active materials, alsosometimes referred to as smart materials, refer to materials orcompositions that have the ability to remember their original shape,which can subsequently be recalled by applying an external stimulus(i.e., an activation signal). Thus, deformation of a shape memorymaterial from its original shape can be a temporary condition.

Exemplary shape memory materials include shape memory alloys (SMAs),electroactive polymers (EAPs) such as dielectric elastomers, ionicpolymer metal composites (IPMC), piezoelectric polymers and shape memorypolymers (SMPs), magnetic shape memory alloys (MSMA), shape memoryceramics (SMCs), baroplastics, piezoelectric ceramics,magnetorheological (MR) elastomers, composites of the foregoing shapememory materials with non-shape memory materials, and combinationscomprising at least one of the foregoing shape memory materials. TheEAPs, piezoceramics, baroplastics, and the like can be employed in asimilar manner as the shape memory alloys described herein, as will beappreciated by those skilled in the art in view of this disclosure.

In the present disclosure, most embodiments include shape memory wires.However, shape memory materials and other active materials may beemployed in a variety of other forms within the scope of the claimedinvention, such as strips, sheets, slabs, foam, cellular and latticestructures, helical or tubular springs, braided cables, tubes orcombinations comprising at least one of the forgoing forms can beemployed in a similar manner as will be appreciated by those skilled inthe art in view of this disclosure.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A method for selectively deploying a head restraint assemblycomprising: activating an active material member with an activationsignal, wherein the active material member includes a first end and asecond end in operative communication with a support member, and whereinthe active material member is configured to undergo a change in at leastone property between the first end and the second end upon receipt ofthe activation signal; and said change in at least one property betweenthe first end and the second end of the active material member therebyactuating a deployable member to move from a retracted position to adeployed position to deploy the head restraint assembly; whereinactuating the deployable member to move from the retracted position tothe deployed position to deploy the head restraint assembly includes:rotating a first link rotatably mounted to the support member and thedeployable member to thereby move the deployable member from theretracted position to the deployed position; rotating a second linkrotatably mounted to the deployable member and a clutch assembly whenthe deployable member moves from the retracted position to the deployedposition; and sliding a clutch along a rod mounted with respect to thesupport member when the second link is rotated.
 2. The method of claim1, further comprising deactivating the active material member to reversethe change in the at least one property of the active material memberbetween the first end and the second end.
 3. The method of claim 1,wherein activating the active material member with the activation signalcomprises applying a selected one of a thermal activation signal, anelectric activation signal, a magnetic activation signal, a chemicalactivation signal, and a mechanical load.
 4. The method of claim 1,wherein the at least one property is shape, stiffness or a dimension ofthe active material member, and wherein the change is in proportion toan applied external signal.
 5. The method of claim 1, wherein thesliding the clutch assembly along the rod further comprises selectivelypreventing movement of the deployable member from the deployed positionto the retracted position.
 6. The method of claim 5, further comprisingselectively releasing the clutch assembly to allow movement of thedeployable member from the deployed position to the retracted position.